Magnetic head and manufacturing method thereof

ABSTRACT

Embodiments of the present invention provide a magnetic head having a read head of stable reading operation and with less magnetic fluctuation noise. According to one embodiment, a free layer has a structure comprising two ferromagnetic layers (a first free layer and a second free layer) that are coupled anti-ferromagnetically by way of a non-magnetic intermediate layer, in which the magnetization amount of the first free layer is set to larger than the magnetization amount of the second free layer. Further, the magnetic domains in the first free layer and the second free layer are stabilized simultaneously by increasing the distance between the second free layer and the magnetic domain control film to be more than the distance between the first free layer and the magnetic domain control film, thereby adjusting the magnetization amount of the magnetic domain control film. Further, the volume of the entire free layer is increased thereby greatly decreasing the magnetic fluctuation noises, to obtain a read head showing a high SN ratio.

CROSS-REFERENCE TO RELATED APPLICATION

The instant nonprovisional patent application claims priority toJapanese Patent Application No. 2008-108925 filed Apr. 18, 2008, andwhich is incorporated by reference in its entirety herein for allpurposes.

BACKGROUND OF THE INVENTION

Generally a magnetic read head includes a pair of upper and lowermagnetic shield layers, a magnetoresistive film disposed therebetween,and a pair of electrodes connected electrically to the magnetoresistivefilm. In the case of magnetic recording and reproducing apparatus havingan areal recording density in excess of 300 Gbits per 1 square inch, ahigh sensitive read device such as a tunneling magnetoresistive film(TMR film) or a current-perpendicular-to-plane giant magnetoresistivefilm (CPP-GMR) is utilized as a magnetoresistive film. Themagnetoresistive film has a free layer, an intermediate layer, and apinned layer, in which the magnetization in the free layer rotates inaccordance with the change of signal magnetic fields from a recordingmedium. On the other hand, the direction of the magnetic moment in thepinned layer is generally fixed. When a sense current is supplied to themagnetoresistive film, a voltage between electrodes of the devicechanges depending on the angle formed between the magnetic moment of thefree layer and the magnetic moment of the pinned layer. The resultingvoltage is detected as a read signal. In the CPP-GMR film, theintermediate layer is a conductor and an oxide or the like is used inthe TMR film.

In the magnetic read head, a magnetic domain control film is disposed onboth ends in the direction of the track width of the free layer formaking the free layer into a single magnetic domain structure orpreventing magnetic domain movement. This configuration aims atpreventing erroneous operation of the recording and reproducingapparatus caused by output fluctuation or the like due to movement ofthe magnetic domain in the case where the magnetic domain of the freelayer undergoes a magnetic effect from the write element, upper andlower magnetic shields, etc. For such a magnetic domain control film, apermanent magnet is generally used (see Japanese Patent Publication No.3-125311 “Patent Document 1”). On the other hand, In the case of the TMRfilm or the CPP-GMR film, it has also been proposed to adopt a structurein which a magnetic domain control film is stacked to a ferromagneticfree layer. In this case, as the magnetic domain control film, apermanent magnet (see Japanese Patent Publication No. 11-259824 “PatentDocument 2”) or a stacked layer of an anti-ferromagnetic layer and aferromagnetic layer (see U.S. Pat. No. 6,023,395 “Patent Document 3”)has been known.

To increase the density of the magnetic recording and reproducingapparatus, it is useful to narrow a recording bit and, for copingtherewith, it is requested to narrow the distance between upper andlower magnetic shields of the magnetic read head and the read trackwidth thereof.

As described above, to improve the recording density of the magneticrecording and reproducing apparatus, the read track width of themagnetic read head has been finely formed. Generally, the read trackwidth is narrower, the read output is lowered. Further, it has beenpointed out that magnetization fluctuation noises become actual as theread device is made finer. The magnetization fluctuation noise is causedby thermal fluctuation of magnetization in the free layer. Generally, asthe volume of a magnetic body decreases, thermal fluctuation ofmagnetization increases. Accordingly, as the device is made finer, thevolume of the free layer is decreased to increase the thermalfluctuation of magnetization in the free layer. Then, a relative anglebetween the magnetization in the free layer and the magnetization in thepinned layer fluctuates greatly, resulting in increased noise. Further,it has a characteristic that the magnetization fluctuation noiseincreases in proportion to the output. This means that unless themagnetization fluctuation noise per se is suppressed, improvement for asignal-to-noise ratio cannot be expected even when the output is merelyincreased.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention provide a magnetic head having aread head of stable reading operation and with less magnetic fluctuationnoise. According to the embodiment of FIG. 1, a free layer has astructure comprising two ferromagnetic layers (free layer 1, free layer2) that are coupled anti-ferromagnetically by way of a non-magneticintermediate layer 19, in which the magnetization amount of the freelayer 1 (18) is set to larger than the magnetization amount of the freelayer 2 (20). Further, the magnetic domains in the free layer 1 (18) andthe free layer 2 (20) are stabilized simultaneously by increasing thedistance Sp2 between the free layer 2 (20) and the magnetic domaincontrol film 41 more than the distance Sp1 between the free layer 1 (18)and the magnetic domain control film 41, thereby adjusting themagnetization amount of the magnetic domain control film 41. Further,the volume of the entire free layer is increased thereby greatlydecreasing the magnetic fluctuation noises, to obtain a read head 100showing a high SN ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged conceptional view of a read head according to anembodiment of the invention at the medium opposing surface.

FIG. 2 is a view showing the distribution of a magnetic domain controlmagnetic field in a free layer of a read head according to an embodimentof the invention.

FIG. 3 is a view showing an electromagnetic response curve of a readhead according to an embodiment of the invention.

FIG. 4 is an enlarged view of a read head according to Embodiment 1 atthe medium opposing surface.

FIG. 5 is a view of a perpendicular recording magnetic head according toEmbodiment 1 at the medium opposing surface.

FIG. 6 is a view schematically showing the state of perpendicularmagnetic recording of a perpendicular recording magnetic head accordingto Embodiment 1.

FIG. 7 is a view of a perpendicular recording magnetic head according toa modified example of Embodiment 1 as viewed at the medium opposingsurface.

FIG. 8 is a schematic perspective view of a longitudinal recordingmagnetic head according to Embodiment 2.

FIG. 9 is a schematic constitutional view of a magnetic disk apparatushaving a magnetic head according to an embodiment mounted thereon.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention relate to a magnetic head used formagnetic recording and reproducing apparatus and a manufacturing methodthereof, and particularly relate to a constitution and a manufacturingmethod of a magnetic read head.

As a structure used to effectively decrease the magnetic fluctuationnoise, a ferri-magnetic free layer has been proposed. In theferri-magnetic free layer, two ferromagnetic layers (free layer 1 andfree layer 2) are stacked by way of a non-magnetic metal to maintainmagnetization of them anti-parallel with each other. Accordingly,effective magnetization is determined by the difference between themagnetization amount in the free layer 1 and the magnetization amount inthe free layer 2. The ferri-magnetic free layer has a feature capable ofdecreasing the effective magnetization while keeping the entire volumeof the free layer. As described above, by increasing the entire volumeof the free layer and decreasing the effective magnetization, a highread sensitivity can be maintained and the magnetization fluctuationnoise can be suppressed.

In the ferri-magnetic free layer, a magnetization direction in a layerof larger magnetization amount (free layer 1) and a magnetizationdirection in a magnetic domain control film are generally aligned.Accordingly, the magnetization direction in the free layer 2 isanti-parallel with respect to the magnetization direction in themagnetic domain control film. Further, since anti-ferromagnetic couplingbetween the free layer 1 and the free layer 2 is infinite, when themagnetic domain control field is large, a region where the magnetizationin the free layer 1 and the magnetization in the free layer 2 cannot bemaintained in anti-parallel with each other is generated. If such aregion is present, the operation of the magnetization in the free layer2 becomes instable upon application of a medium signal magnetic field tocause increase of the noise and fluctuation of the read output. On theother hand, if the magnetic domain control field is weak, the operationof the free layer 1 becomes instable. That is, it is difficult in thecurrent magnetic domain control structure to stably control the freelayer 1 and the free layer 2 of the ferri-magnetic free layersimultaneously.

As described above, even when a ferri-magnetic free layer capable ofeffectively suppressing the magnetic fluctuation noise is used, theincrease of the noise and instability of the head operation may occur inthe current magnetic domain control structure. If such a magnetic headwere assembled into a magnetic recording and reproducing apparatus, itis apparent that the apparatus would not operate normally.

An object of embodiments of the present invention is to provide amagnetic head with less magnetic fluctuation noise during reading andwith stable operation.

Another object of embodiments of the invention is to provide a method ofmanufacturing a magnetic head with less magnetization fluctuation noiseduring reading and with stable operation.

To attain the purpose described above, the magnetic head of embodimentsof the invention comprises: a lower magnetic shield layer; an uppermagnetic shield layer; a magnetoresistive film disposed between thelower magnetic shield layer and the upper magnetic shield layer andhaving a pinned layer, an intermediate layer and a free layer; and amagnetic domain control film disposed on both ends in the direction ofthe track width of the magnetoresistive film. The free layer has a freelayer 1 and a free layer 2 stacked by way of a non-magnetic intermediatelayer. The free layer 1 is stacked by way of the intermediate layer tothe pinned layer. Magnetization in the free layer 1 and magnetization ofthe free layer 2 are in anti-parallel with each other. The magnetizationamount in the free layer 1 is larger than the magnetization amount inthe free layer 2. Further, Sp2>Sp1 is satisfied assuming a distancebetween the free layer 1 and the magnetic domain control film as Sp1 anda distance Sp2 between the free layer 2 and the magnetic domain controlfilm as Sp2.

The relationship between the Sp1 and the Sp2 may be Sp2>2×Sp1. In oneembodiment, Sp1 is a distance between the center of the free layer 1 inthe direction of its thickness and the magnetic domain control film, andSp2 is a distance between the center of the free layer 2 in thedirection of its thickness and the magnetic domain control film.

A lower electrode layer may be present above the lower magnetic shieldlayer, and an upper electrode layer may be present below the uppermagnetic shield layer. Each of the free layer 1 and the free layer 2 maycomprise two or more ferromagnetic layers by way of a non-magnetic metallayer and magnetizations in each of the ferromagnetic layers are inparallel with each other.

The non-magnetic intermediate layer may be at least one element selectedfrom the group consisting of Ta, Cu, Ru, Cr, Ir, and Rh.

A read/write head can be constituted by providing a read head adjacentto the upper magnetic shield layer.

To attain the object described above, a magnetic head according toembodiments of the invention may comprise: a lower magnetic shieldlayer; an upper magnetic shield layer; a magnetoresistive film disposedbetween the lower magnetic shield layer and the upper magnetic shieldlayer and having a pinned layer, an intermediate layer, and a freelayer; and a magnetic domain control film disposed on both ends in thedirection of the track width of the magnetoresistive film. The freelayer has a free layer 1 and a free layer 2 stacked by way of anon-magnetic intermediate layer. The free layer 1 is stacked by way ofthe intermediate layer to the pinned layer. Magnetization in the freelayer 1 and magnetization in the free layer 2 are in anti-parallel witheach other. The product of a saturation magnetic flux density of thefree layer 1 and a thickness of the free layer 1 (Bs·t)₁ is larger thanthe product of a saturation magnetic flux density of the free layer 2and a thickness of the free layer 2 (Bs·t)₂. Further,(Br·t)_(PM)≧(9×Sp1/ts)×{(Bs·t)₁−(Bs·t)₂} and H_(AF2)>H_(bias2) aresatisfied when assuming a distance between the free layer 1 and themagnetic domain control film as Sp1, a distance between the free layer 2and the magnetic domain control film as Sp2, a distance between the freelayer 1 and the upper magnetic shield as ts, the product of the residualmagnetic flux density and the film thickness of the magnetic domaincontrol film as (Br·t)_(PM), an anti-ferromagnetic coupling fieldapplied to the free layer 2 as H_(AF2), and the magnetic domain controlfield applied to the free layer 2 as H_(bias2).

The relation H_(AF2)>H_(bias2) is attained by defining the relationbetween the Sp1 and the Sp2 as Sp2>Sp1.

To attain another object of embodiments of the invention, a method ofmanufacturing a magnetic head of one embodiment of the inventionincludes the steps of: forming a lower magnetic shield layer; stacking apinned layer, an intermediate layer, a free layer 1, a non-magneticintermediate layer, and a free layer 2 above the lower magnetic shieldlayer thereby forming a magnetoresistive film, in which magnetization inthe free layer 1 and magnetization in the free layer 2 are inanti-parallel with each other, and the magnetization amount in the freelayer 1 is larger than the magnetization amount in the free layer 2;forming a magnetic domain control film on both ends in the direction ofthe track width of the magnetoresistive film, in which Sp2>Sp1 issatisfied when assuming a distance between the center of the free layer1 in the direction of its thickness and the magnetic domain control filmas Sp1 and a distance between the center of the free layer 2 in thedirection of its thickness and the magnetic domain control film as Sp2;and forming an upper magnetic shield layer above the magnetoresistivefilm and the magnetic domain control film.

The step of forming the magnetic domain control film includes a step ofcontrolling the incident direction of sputtered magnetic particles so asto satisfy Sp2>Sp1.

The step of forming the magnetic domain control film includes a step offorming a hard magnetic film and a step of patterning the hard magneticfilm so as to satisfy the Sp2>Sp1 by ion milling.

According to embodiments of the invention, since the magnetic domaincontrol field applied to the free layer 2 can be decreased whilesufficiently ensuring the magnetic domain control field applied to thefree layer 1 in the laminated ferri-magnetic free layer, it is possibleto provide a magnetic head capable of magnetic domain control for thefree layer 1 and the free layer 2 simultaneously and sufficiently,suppressed sufficiently for the magnetization fluctuation noise andhaving stable operation.

First, the magnetic head according to one embodiment of the invention isdescribed with reference to FIG. 1. FIG. 1 is a conceptual view of aread head as viewed at the opposing surface of a medium. In FIG. 1, onlythe upper and lower magnetic shield layers, a magnetic domain controlfilm and a ferri-magnetic free layer are shown. Further, for the sake ofsimplicity of description, only one of the pair of magnetic domaincontrol films is illustrated. A non-magnetic intermediate layer isdisposed between a free layer 1 and a free layer 2, and magnetization inthe free layer 1 and the magnetization in the free layer 2 are stronglycoupled anti-ferromagnetically. They are stacked to each other so as toattain (Bs·t)₁>(Bs·t)₂ assuming the magnetization amount (product ofsaturation magnetic flux density and film thickness) of the free layer 1and the free layer 2 as (Bs·t)₁ and (Bs·t)₂, respectively. For keepingthe magnetization in the free layer 1 and the magnetization in the freelayer 2 substantially in anti-parallel with each other, the differencebetween the magnetization amounts (Bs·t)₁−(Bs·t)₂ may be 1T nm or more.In this case, the directions for the magnetization of the magneticdomain control film and the magnetization in the free layer 1 aresubstantially aligned. On the other hand, the magnetization of themagnetic domain control film and the direction of the magnetization inthe free layer 2 are in the direction contrary to each other.

In the case where the magnetic domain control field applied to the freelayer 2 exceeds the anti-ferromagnetic coupling field between the freelayer 1 and the free layer 2, the magnetization in the free layer 2 isin a direction identical with that of the magnetic domain control field.In such a case, the ferri-magnetic free layer structure is no moreattained and the read sensitivity is also lowered extremely.Accordingly, it is necessary that the magnetic domain control field isless than the anti-ferromagnetic coupling field applied to the freelayer 2.

Assuming the distance between the center of the free layer 1 in thedirection of the film thickness and the magnetic domain control film asSp1 and the distance between the center of the free layer 2 in thedirection of the film thickness and the magnetic domain control film asSp2, a case where Sp1=Sp2 is considered first. In this case, themagnetic domain control field applied to the free layer 1 and themagnetic domain control field applied to the free layer 2 aresubstantially equal with each other. Then, the magnetization in the freelayer 1 and the magnetic domain control field are in the identicaldirection, and if the magnetic domain control field is ensuredsufficiently, the magnetic domain of the free layer 1 is made stable orformed as a single magnetic domain. On the other hand, magnetization inthe free layer 2 is in a direction opposite to that of the magneticdomain control field and the net magnetic field applied to the freelayer 2 is a difference formed by subtracting the magnetic domaincontrol field from the anti-ferromagnetic coupling field. Accordingly,when the magnetic domain control field is strong, the net magnetic fieldapplied to the free layer 2 is decreased and the magnetic domain in thefree layer 2 is no more stabilized. After all, at Sp1=Sp2, it isdifficult to simultaneously stabilize the magnetic domains in the freelayer 1 and the free layer 2.

Then, the magnetic domain control film is formed so as to attainSp2>Sp1. When the Sp1 is narrowed, the magnetic domain control fieldapplied to the free layer 1 can be increased. At the same time, when Sp2is made wider, control can be conducted so as to decrease the magneticdomain control field applied to the free layer 2.

Specifically, assuming the distance between the free layer 1 and theupper magnetic shield as ts and the amount of magnetization of themagnetic domain control film (product of residual magnetic flux, densityand film thickness) as (Br·t)_(PM), and Sp1 and (Br·t)_(PM) arecontrolled so as to satisfy (Br·t)_(PM)≧(9×Sp1/ts)×{(Bs·t)₁−(Bs·t)₂},the magnetic domain in the free layer 1 is stabilized. On the otherhand, assuming the anti-ferromagnetic coupling field applied to the freelayer 2 as H_(AF2) and the magnetic domain control field applied to thefree layer 2 as H_(bias2), magnetic domain in the free layer 2 isstabilized by controlling Sp2 so as to satisfy H_(AF2)>H_(bias2). Then,the foregoings are to be explained quantitatively with reference to theresult of simulation.

FIG. 2 shows the result of calculation for the distribution of themagnetic domain control field H_(bias2) (hard bias field) in each of thefree layers. The zero point on the abscissa of a graph shown in FIG. 2represents the track end of the free layer. In FIG. 2, it is set asGs=36 nm, Sp1=5 nm, Sp2=10 nm, (Br·t)_(PM)=16T nm, (Bs·t)₁=5T nm,(Bs·t)₂=2T nm, and ts=5 nm. In this case, Gs is a distance between theupper magnetic shield layer and the lower magnetic shield layer. In viewof FIG. 2, it can be seen that H_(bias) reaches the maximum at the trackend and decays as it approaches to the track center in the free layer 1.On the other hand, in the free layer 2, H_(bias) reaches the maximum ofa position somewhat inside from the track end and decays as it furtherapproaches the track center.

Then, with use to the result of FIG. 2, micromagnetics simulation wasperformed by using an LLG (Landau-Lifshits-Gilbert) equation. In thesimulation, it was set as H_(AF2)=1500 Oe (120 kA/m). As a result, ithas been found that the magnetization in the free layer 1 and the freelayer 2 operates stably. Further, identical micromagnetics simulationwas performed with Sp2 being less than 10 nm, but it has been found thatmagnetization in the free layer 2 did not operate stably. Accordingly,since H_(AF2)=1500 Oe (120 kA/m) and the maximum value of H_(bias2) is1370 Oe (110 kA/m), it can be seen that the relation H_(Af2)>H_(bias2)is satisfied. Further, an optimal value of (Br·t)_(PM) was investigatedby calculating a transfer curve (electromagnetic response curve).Generally, (Br·t)_(PM) necessary for stabilizing the magnetic domain inthe free layer is represented by (Br·t)_(PM)≧F×{(Bs·t)₁−(Bs·t)₂}, andF≧1. F is a shape factor depending on the position for the magneticdomain control and the head structure. F=1 in the case where Gs or ts issufficiently large, Sp1=0 nm, and the non-magnetic intermediate layer issufficiently small. In this case, magnetic charges induced to the end ofthe free layer in the direction of the track are completely offset bythe magnetic domain control field. However, in an actual head, the freelayer and the magnetic domain control film are separated by a finitedistance. Further, when Gs or ts is narrowed, the magnetic domaincontrol field is absorbed in the shield. Accordingly, it is necessary toincrease (Br·t)_(PM) (F>1). Since the magnetic domain control fieldincreases as Sp1 is decreased and decreases as ts is narrowed,(Br·t)_(PM) necessary for stabilizing the magnetic domain of the freelayer can be represented as (Br·t)_(PM)>(G×Sp1/ts){(Bs·t)₁−(Bs·t)₂}. Thecoefficient G has a relation with F as G=F/(Sp1/ts). FIG. 3 shows atransfer curve relative to the value for each G. As can be seen fromFIG. 3, hysteresis occurs in the transfer curve at G<9. Such hysteresiscauses output fluctuation or instability of the operation of theapparatus. On the other hand, at G≧9, no abnormality is found in thetransfer curve. From the result described above, it can be seen that theoperation of the magnetization in the free layer 1 and the free layer 2are stabilized simultaneously when they satisfy relations(Br·t)_(PM)≧(9×Sp1/ts)×{(Bs·t)₁−(Bs·t)₂} and Sp2>2×Sp1.

As described above, stable operation was confirmed in the ferri-magneticfree layer structure. In the ferri-magnetic free layer, the entirevolume or the entire amount of magnetization can be increased whilemaintaining the difference of the magnetization constant between thefree layer 1 and the free layer 2 constantly. In this case, thetheoretical equation for the magnetic fluctuation noise is given by thefollowing equation:

$V_{mag} = {\frac{I_{s}\Delta \; R}{H_{stiff}}\sqrt{\frac{\alpha \; k_{B}T}{\mu_{0}M_{s}V\; \gamma}}}$

Here, Vmag is the magnetic fluctuation noise voltage, I_(s) is a sensingcurrent, ΔR is an amount of change of resistance, Hsiff is stiffnessmagnetic field, α is decay constant, k_(B) is Boltzmann constant, T istemperature, μ₀ is magnetic permeability in vacuum, Ms is saturationmagnetization, V is volume, and γ is magnetization rotation ratio. Ascan be seen from the equation described above, the magnetizationfluctuation noise voltage is in inverse proportion to the square root ofthe volume of the magnetic body. In this case, the entire magnetizationamount in the free layer of the read head according to the invention isset to 2 to 3 times as large as the amount of the existent head. It canbe seen that the magnetization fluctuation noise can be decreased, inthe read head of the invention, to 0.58 to 0.7 times compared with thatof the existent head. On the other hand, in the ferri-magnetic freelayer, since the utilization factor of the head can be maintained higheven when the entire magnetization amount is increased, lowering of theoutput as seen in the existent head does not occur. Even when amagnetoresistive film showing the magnetoresistive ratio identical withthat of an existent head is used, the signal-to-noise ratio of the readhead according to embodiments of the invention is estimated to be higherby 3 to 5 dB. Particular embodiments of the invention are describedbelow.

Embodiment 1

In Embodiment 1, a magnetic domain control film and a magnetoresistivefilm are formed so as to satisfy(Br·t)_(PM)≧(9×Sp1/ts)×{(Bs·t)₁−(Bs·t)₂} and Sp2>2×Sp1. As themagnetoresistive film, a current-perpendicular-to-plane TMR film wasadopted. A permanent magnet was disposed as the magnetic domain controlfilm to both ends in the direction of the track width of themagnetoresistive film.

FIG. 4 is an enlarged view of a read head according to Embodiment 1 atthe surface opposing to a recording medium. A read head 100 has a lowermagnetic shield layer 1 comprising NiFe or the like of 3 μm thicknessdisposed by way of base alumina on a substrate (not illustrated), alower electrode layer 3 disposed on the lower magnetic shield layer 1, aTMR film 10 disposed above the lower electrode layer 3, a magneticdomain control film 41 disposed on both ends in the direction of thetrack width of the TMR film 10, an upper electrode layer 4 disposedabove the TMR film 10 and above the magnetic domain control film 41, andan upper magnetic shield layer 2 comprising NiFe or the like of 2 μmthickness disposed on the upper electrode layer 4. In the constitutiondescribed above, the lower electrode layer 3 and the upper electrodelayer 4 are electrically connected with the TMR film 10. An insulativelayer 30 is disposed at the periphery of the TMR film 10, and betweenthe magnetic domain control film 41 and the upper and lower electrodelayers 3, 4. In the constitution described above, the lower magneticshield 1 may be constituted also as the lower electrode layer 3, and theupper magnetic shield 2 may be constituted also as the upper electrodelayer 4.

The TMR film 10 includes, from the side of the lower magnetic shieldlayer 1, an underlayer 12, an anti-ferromagnetic layer 13 comprisingMnPt or the like of 15 nm thickness, a first ferromagnetic pinned layer14 comprising NiFe or the like of 2 nm thickness, a non-magneticseparation layer 15 comprising Ru or the like of 1 nm thickness, asecond ferromagnetic pinned layer 16 comprising NiFe or the like of 3 nmthickness, a barrier layer 17 comprising alumina or the like of 1 nmthickness, a free layer 1 (18) comprising NiFe or the like of 5 nmthickness, a non-magnetic intermediate layer 19 comprising Ru or thelike of 0.8 nm thickness, a free layer 2 (20) comprising NiFe or thelike of 2 nm thickness, and a cap layer 21. The first ferromagneticpinned layer 14, the non-magnetic separation layer 15, and a secondferromagnetic pinned layer 16 constitute a pinned layer. In the exampledescribed above, the TMR film 10 is used as the magnetoresistive film,but a CPP-GMR film may also be used instead of the TMR film. Further,the anti-ferromagnetic layer 13 may be saved depending on the case.

Thin film constituting the TMR film or the CPP-GMR film was prepared asdescribed below by an RF magnetron sputtering apparatus. It was preparedby successively stacking the following materials to a ceramic substrateof 1 mm thickness in an Ar gas atmosphere of 1 to 6 mm Torr. As asputtering target, each of targets of Ta, Ni-20 at % Fe alloy, Cu, Co,MnPt, Ru, alumina, and NiMn was used. Chip of Fe and Ni each of 1 cmsquare were properly arranged on the Co target to adjust control thecomposition. Each of the layers of the stacked film was formedsuccessively by generating plasmas in an apparatus while applying an RFpower to cathodes disposed with each of the targets and by opening andclosing shutters provided on every cathode one by one. During filmformation, a magnetic field of about 640 A/m was applied in parallelwith the substrate by using a permanent magnet to provide monoaxialanisotropy. A heat treatment at 270° C. for 3 hr was applied to theformed film under vacuum in the magnetic field to cause phasetransformation to the MnPt anti-ferromagnetic layer 13, and thenmagnetic resistance at a room temperature was measured and evaluated.

The TMR film 10 was prepared by patterning such that the width in thedirection of the track width of the barrier layer 17 had a desiredvalue. It was set to 80 nm in this embodiment. In the patterning, aphotoresist or the like formed to a predetermined width was disposedover the TMR film before patterning, and by using this as a mask,unnecessary portion was etched. Then, a hard magnetic film as a magneticdomain control film 41 comprising CoCrPt or the like of about 40 nmthickness was formed on both ends in the direction of the track width ofthe TMR film 10. The shape of the hard magnetic film was adjusted suchthat Sp2=5 nm and Sp1=10 nm. The shape of the hard magnetic film wasattained by adjusting the height of the resist mask and the incidentdirection of sputtered particles upon ion beam sputtering.Alternatively, after forming an insulative film and a hard magnetic filmin the direction of the track width, it may be etched again into adesired shape by ion beam. After the heat treatment, a magnetizingtreatment for the hard magnetic film was conducted at a room temperatureto form a permanent magnet as the magnetic domain control film 41. A gapGs between the upper magnetic shield layer 2 and the lower magneticshield layer 1 at a portion where the TMR film 10 was disposed was about36 nm.

In Embodiment 1 described above, while the free layer 1 and the freelayer 2 each are a single layer comprising NiFe or the like, they may bea multi-layered film constituted with two or more of ferromagneticlayers by way of a non-magnetic metal layer, in which magnetizations ofthe ferromagnetic layers are in parallel with each other. Further, whileRu was used for the non-magnetic intermediate layer, it may be at leastone element selected from the group consisting of Ta, Cu, Ru, Cr, Ir andRh.

FIG. 5 shows a constitution of a perpendicular recording magnetic head180 comprising the read head 100 manufactured as described above and aperpendicular magnetic write head 150 in combination as viewed at thesurface opposing to a medium. The perpendicular magnetic write head 150has a sub pole 72 comprising an NiFe alloy or the like of about 2 μmthickness disposed by way of a non-magnetic separation layer 6comprising alumina or the like of 500 nm thickness above the read head100, and a main pole 71 comprising an FeCo alloy or the like of 200 nmthickness disposed by way of a magnetic gap 73 above the sub pole 72. Acoil 80 is disposed between the main pole 71 and the sub pole 72 (referto FIG. 6). The main pole 71 is formed as an inverted trapezoidal shapewith a wide upper width and a narrow lower width, in which the upperwidth 53 is about 130 nm. A distance between the main pole 71 and thesub pole 72 (thickness for magnetic gap 73) in an air bearing surface(ABS) is about 5 μm.

FIG. 6 schematically shows the state of perpendicular magnetic recordingusing the magnetic head 180 as described above. A recording magneticfield 101 is generated in a magnetic gap between the main pole 71 andthe sub pole 72 by supplying a recording current in a desired pattern tothe coil 80 between the main pole 71 and the sub pole 72, which isapplied in a desired pattern to a perpendicular magnetic recordingmedium 200 thereby writing magnetization information 201 on a recordinglayer 210. For effective use of the magnetic field generated by the mainpole 71, a non-magnetic separation film 230 of about 5 nm thickness isformed under the recording layer 210 and a soft magnetic underlayer 220of about 200 nm thickness is formed therebelow. Further, information isread by detecting a magnetic field leaking from the magnetizationinformation 201 written into the recording layer 210 by the TMR film 10.

The magnetic head 180 of Embodiment 1 was caused to fly such that amagnetic spacing relative to the perpendicular magnetic recording medium200 was 12 nm, and read/write characteristics thereof were evaluated.For confirming the stability of the reading operation, read/writeoperation was conducted repetitively to measure the change of the readoutput. The fluctuation of the read output was satisfactory as 2.5%relative to repetitive read/write for 1,000,000 cycles. In this case,fluctuation of the read output was defined as a value obtained bydividing the difference between the maximum value and the minimum valueof the read output by an average value. From the result, it has beenfound that stable reading operation was conducted. Then, when an SNratio of the read head 100 was measured, it showed a high value of about31 dB. Noises used in the calculation of the SN ratio of the read headare those obtained by subtracting medium noises from total noises. Forcomparison, a magnetic head of an existent structure was manufactured inan identical device size by using an identical magnetoresistive film,and read/write characteristics were evaluated. As a result, the readhead SN ratio was about 28 dB which was a value lower by 3 dB comparedwith the magnetic head of the embodiment. As described above, accordingto this embodiment, a magnetic head of stable reading operation andshowing high SN ratio can be obtained.

FIG. 7 shows a modified example of the magnetic head according toEmbodiment 1. A magnetic head 180′ is of a constitution having awrap-around shield 74 around a main pole 71 and other constitutions areidentical with those in Embodiment 1. The wrap-around shield 74 is amagnetic shield disposed on the trailing side and both sides of the mainpole 71 integrally. By the provision of the wrap-around shield 74, themagnetic field gradient of the recording magnetic field from the mainpole 71 can be made abrupt to suppress recording blurring in thedirection of the track width. As a matter of fact, the function isidentical with a case where a trailing shield and a side shield areformed separately. The wrap-around shield 74 is formed by forming amagnetic layer comprising NiFe or the like by way of a non-magneticlayer such as alumina above and on both sides of the main pole 71.

Embodiment 2

FIG. 8 shows a schematic perspective cross sectional view of a magnetichead according to Embodiment 2. A magnetic head 300 is a magnetic headfor longitudinal magnetic recording and comprises the read head 100 ofEmbodiment 1 and a longitudinal magnetic write head 310 in combination.The longitudinal magnetic write head 310 has a lower core 50 disposedabove the read head 100 by way of a non-magnetic separation layer 54comprising alumina or the like of 500 nm thickness, an upper core 51,and a coil 52 for generating a magnetic flux disposed between the cores.A recording magnetic field is generated in a recording gap between theupper and lower cores 51, 50 by supplying a writing current in a desiredpattern to the coil 52, which is applied in a desired pattern to amagnetic medium to write a magnetization information having a desiredmagnetizing direction to the magnetic medium. Further, information isread by detecting the magnetic field leaking from the magnetizationinformation written in the magnetic medium by a magnetoresistive film10. Also in the magnetic head, reading operation is stable and high SNratio is shown.

FIG. 9 is an example for the constitution of a magnetic recording diskapparatus having, mounted thereon, a magnetic head according toEmbodiment 1 or a modification example thereof, or Embodiment 2. A disk95 holding a recording medium 96 for magnetically recording informationis rotated by a spindle motor 93, and a head slider 90 is guided onto atrack of the disk 95 by an actuator 92. That is, in the magnetic diskapparatus, a magnetic head according to Embodiment 1 or a modificationexample thereof, or Embodiment 2 formed above the head slider 90conducts relative movement in proximity to a predetermined recordingposition on the disk 95 by the actuator 92 to successively write andread signals. The actuator 92 may be a rotary actuator. Recordingsignals are recorded by way of a signal processing system 94 on themedium by a write head, and the output of the read head is obtained assignals by way of the signal processing system 94. Further, upon movingthe head slider 90 to a desired recording track, the head slider 90 canbe positioned by detecting the position on the track by using a highsensitive output and controlling the actuator 92. In FIG. 9, while thehead slider 90 and the disk 95 are shown each by one, they may also bedisposed in plurality. Further, information may be recorded on the disk95 having recording medium 96 on both sides thereof. In the case whereinformation is recorded on both sides of the disk, the head slider 90 isdisposed on both sides of the disk. The magnetic disk apparatus canattain high recording density by mounting the magnetic head according toeach of the embodiments described above. Further, by mounting aperpendicular magnetic write head and a perpendicular magnetic recordingdisk according to Embodiment 1 or the modification example, a magneticdisk apparatus having an in-plane recording density of more than 300Gbits per 1 square cm can be attained.

1. A magnetic head comprising: a lower magnetic shield layer; an uppermagnetic shield layer; a magnetoresistive film disposed between thelower magnetic shield layer and the upper magnetic shield layer, themagnetoresistive film having a pinned layer, an intermediate layer, anda free layer; and a magnetic domain control film disposed on both endsin the direction of the track width of the magnetoresistive film;wherein the free layer has a first free layer and a second free layerstacked with a non-magnetic intermediate layer between, the first freelayer being stacked on the intermediate layer over the pinned layer,magnetization in the first free layer and magnetization in the secondfree layer being in anti-parallel with each other, and a magnetizationamount of the first free layer being larger than a magnetization amountof the second free layer, and wherein Sp2>Sp1 is satisfied when assuminga distance between the first free layer and the magnetic domain controlfilm is Sp1, and a distance between the second free layer and themagnetic domain control film is Sp2.
 2. The magnetic head according toclaim 1, wherein the relation between Sp1 and Sp2 is Sp2>2×Sp1.
 3. Themagnetic head according to claim 1, wherein the Sp1 is a distancebetween the center of the first free layer in the direction of itsthickness and the magnetic domain control film, and the Sp2 is adistance between the center of the second free layer in the direction ofits thickness and the magnetic domain control film.
 4. The magnetic headaccording to claim 1, comprising a lower electrode layer disposed abovethe lower magnetic shield layer, and an upper electrode layer disposedbelow the upper magnetic shield layer.
 5. The magnetic head according toclaim 1, wherein the free layer 1 and the second free layer eachcomprise two or more ferromagnetic layers by way of a non-magnetic metallayer, and magnetizations in each of the ferromagnetic layers are inparallel with each other.
 6. The magnetic head according to claim 1,wherein the non-magnetic intermediate layer is at least one elementselected from the group consisting of Ta, Cu, Ru, Cr, Ir, and Rh.
 7. Themagnetic head according to claim 1, comprising a write head disposedadjacent to the upper magnetic shield layer.
 8. A magnetic headcomprising: a lower magnetic shield layer; an upper magnetic shieldlayer; a magnetoresistive film disposed between the lower magneticshield layer and the upper magnetic shield layer, the magnetoresistivefilm having a pinned layer, an intermediate layer and a free layer; anda magnetic domain control film disposed on both ends in the direction ofthe track width of the magnetoresistive film; wherein the free layer hasa first free layer and a second free layer stacked with a non-magneticintermediate layer between, the first free layer being stacked on theintermediate layer over the pinned layer, magnetization in the firstfree layer and magnetization of second free layer being in anti-parallelwith each other, and a product of a saturation magnetic flux density ofthe first free layer and a thickness of the first free layer (Bs·t)₁being larger than a product of a saturation magnetic flux density of thesecond free layer and a thickness of the second free layer (Bs·t)₂, andwherein (Br·t)_(PM)≧(9×Sp1/ts)×{(Bs·t)₁−(Bs·t)₂} and H_(AF2)>H_(bias2)are satisfied when a distance between the first free layer and themagnetic domain control film is Sp1, a distance between the second freelayer and the magnetic domain control film is Sp2, a distance betweenthe first free layer and the upper magnetic shield is ts, a product ofthe residual magnetic flux density of the magnetic domain control filmand a thickness of the magnetic domain control film as (Br·t)_(PM), ananti-ferromagnetic coupling field to be applied to the second free layeris H_(AF2), and the magnetic domain control field to be applied to thesecond free layer as H_(bias2).
 9. The magnetic head according to claim8, wherein the relation between the Sp1 and the Sp2 is Sp2>Sp1 forsatisfying H_(AF2)>H_(bias2).
 10. The magnetic head according to claim9, wherein the relation between the Sp1 and the Sp2 is Sp2>2×Sp1. 11.The magnetic head according to claim 8, wherein the Sp1 is a distancebetween the center of the first free layer in the direction of itsthickness and the magnetic domain control film, and the Sp2 is adistance between the center of the second free layer in the direction ofits thickness and the magnetic domain control film.
 12. The magnetichead according to claim 8, comprising a lower electrode layer disposedabove the lower magnetic shield layer, and an upper electrode layerdisposed below the upper magnetic shield layer.
 13. The magnetic headaccording to claim 8, comprising a write head adjacent to the uppermagnetic shield layer.
 14. A method of manufacturing a magnetic headcomprising the steps of: forming a lower magnetic shield layer; stackinga pinned layer, an intermediate layer, a first free layer, anon-magnetic intermediate layer, and a second free layer above the lowermagnetic shield layer thereby forming a magnetoresistive film, in whichmagnetization in the first free layer and magnetization in the secondfree layer are in anti-parallel with each other, and the magnetizationamount in the first free layer is larger than the magnetization amountin the second free layer; forming a magnetic domain control film on bothends in the direction of the track width of the magnetoresistive film,in which Sp2>Sp1 is satisfied when assuming a distance between thecenter of the first free layer in the direction of its thickness and themagnetic domain control film is Sp1 and a distance between the center ofthe second free layer in the direction of its thickness and the magneticdomain control film is Sp2; and forming an upper magnetic shield layerabove the magnetoresistive film and the magnetic domain control film.15. The manufacturing method of a magnetic head according to claim 14,wherein the step of forming the magnetic domain control film includes astep of controlling the incident direction of sputtered magneticparticles so as to satisfy Sp2>Sp1.
 16. The manufacturing method of amagnetic head according to claim 14, wherein the step of forming themagnetic domain control film includes a step of forming a hard magneticfilm and a step of patterning the hard magnetic film by ion milling soas to satisfy Sp2>Sp1.